Encephalitis

Question 1

what is the definition of encephalitis?

Answer 1

Encephalitis is defined as inflammation of the brain parenchyma associated with neurological dysfunction, such as altered state of consciousness, seizures, personality changes, cranial nerve palsies, speech problems, and motor and sensory deficits.

Question 2

what is the aetiology of encephalitis?

Answer 2

Caue only known in around 50% of cases
Viral infection -herpes, enteroviruses, parechovirus, flaviviruses
Bacterial infection - neisseria meningitidis, TB, syphilis

Question 3

what are the risk factors for encephalitis?

Answer 3

Babies or elderly 
Immunodeficient 
Post infection 
Blood of fluid exposure
Organ transplants 
Bites from animals 
Location / season 
Swimming in freshwater

Question 4

what are the key presentations of encephalitis?

Answer 4

Fever 
Rash 
Altered mental state
Focal neurological deficit
Meningitis

Question 5

what are the first line and gold standard investigations for encephalitis?

Answer 5

FBC - high WBC
Peripheral blood smear - detection of Plasmodium falciparum and Ehrlichia
Serum electrolytes - hyponatremia
Liver functions - elevated
Blood cultures - detection and confirmation of systemic bacterial infections and most arboviral infections
Throat swab - viruses
Nasopharyngeal aspirate - resp viruses
Sputum sample - detection of Mycoplasma, tuberculosis (acid-fast stain), and fungal infections
Chest radiography - TB or sarcoid
CT brain - frequently normal early in the clinical course of encephalitis, but may see more prominent changes
MRI brain - depends on aetiology; often hyperintense lesions (T2 and fluid attenuated inversion recovery [FLAIR] sequences), increased diffusion on diffusion-weighted imaging (DWI) indicating oedema, contrast enhancement on T1 post-contrast sequences indicating blood-brain barrier breakdown; MRI is normal in up to a third of patients with autoimmune encephalitis.
EEG - often shows background slowing
CSF fluid analysis, culture, serology and PCR

Question 6

what are the differential diagnoses of encephalitis?

Answer 6

Aseptic meningitis
Encephalopathy
Status epilepticus

Question 7

how is encephalitis managed?

Answer 7

Viral:
Aciclovir
Other:
Treatment based on aetiology